How to Store Fresh Vegetables

You can learn the best crops to grow or buy, and how to store fresh vegetables year round.

By David Cavagnaro

| December 2004/January 2005

Cabbages are stored most successfully by being replanted in groups in large pots for placement in a cold, moist root cellar.

Photo courtesy David Cavagnaro

When I first contemplated moving from mild coastal California to northeast Iowa, a land of 35-degree-below-zero winters, a major concern was the prospect of giving up homegrown, year-round, fresh vegetables. Not so! A stubborn refusal to relinquish my California ways, combined with the joy of discovering root cellaring and other storage and season-extending techniques, has kept my family (and lots of neighbors) supplied with a long list of garden-fresh vegetables through eight dormant months of northern Iowa winter.

Storing potatoes, root crops and cabbages has a long history in the North, but serving fresh salads in March made with delicate greens such as Chinese cabbage and radicchio harvested the previous October inspires exclamations of amazement and surprise from old-timers and newcomers alike. Learning how to store fresh vegetables year round is a gift that keeps on giving.

Outdoor Food Storage

In all regions of the country, cold-hardy vegetables can simply be left in the ground at the end of the season; it’s only a matter of how long they will survive. In the North, where winters are severe, cabbage, kale, collards, Brussels sprouts and leeks will remain in reasonably good shape in the garden through temperatures well into the teens, and for a while longer, down to about zero. Depending on the winter, this simple technique of neglect may extend the greens season well into December. Carrots, beets and other root crops can be left in the ground, too, under a thick, protective layer of leaves or straw bales. As long as the ground is prevented from freezing, these vegetables can be dug from beneath the snow all winter. Of all the common root crops, only parsnips and Jerusalem artichokes (sunchokes) will survive deep-winter cold without damage, but, of course, the ground still must be kept thawed in order to dig them.

Folks lacking a root cellar or other sufficiently cold place for sustained indoor storage can devise simple techniques to store harvested veggies outdoors. During our first years in Iowa, we dug our Brussels sprout plants in November, stripped off all of the leaves, laid the logs of sprouts side by side on a bed of dry leaves with the roots buried in a shallow trench, then covered them with a thick layer of blankets or old sleeping bags. Thus protected, the insulated veggies stayed fresh and unfrozen all winter under a good snow cover; all we had to do was shovel off a bit of snow, lift back the blankets and cut off a meal of sprouts any time we felt like it.

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Cabbages are stored most successfully by being replanted in groups in large pots for placement in a cold, moist root cellar.Photo courtesy David Cavagnaro

Most winter squash keep nicely in a cool, dry corner or closet.Photo courtesy David Cavagnaro

Trim back the tops and knock the dirt off of freshly harvested leeks, and then pack as many as you can fir into large pots, repacking the soil around the roots as you fill the pots. Water thoroughly, let drain and store in the cold-and-moist section of your root cellar.Photo courtesy David Cavagnaro

For root cellar storage, pack carrots, beets and celeriac roots in sand, and keep them cold (between 32 and 40 degrees) and very moist (90-percent to 95-percent relative humidity).Photo courtesy David Cavagnaro

Quick outdoor storage can be achieved by digging a pit, filling it with cold-hardy crops such as carrots, parsnips, rutabagas, beets, leeks and cabbage, covering the pit with a piece of plywood, then layering the lid and a bit of margin with straw bales. Shoveling snow and moving bales at 20 below zero may not sound like a lot of fun, but it need not be so grim a task. Do this outdoor work on a warmer winter day (We do have them occasionally in the North!) and stock your fridge’s hydrator for the cold spells ahead.

This kind of storage facility creates quite a stir of excitement in the mouse community, I might add, so you will have to mouse-proof your veggies. I suggest setting traps, remembering to devise some way to keep them away from probing fingers. While mixing mouse bait with food may sound tricky, I have successfully placed wax-impregnated brands of bait sticks inside cans or jars, and situated these containers in such a way that the poison and the food cannot mix.

Cold-Frame Season Extender

We use a cold frame for starting plants outdoors in the spring, beginning about the first of April. Heated by sunshine in the daytime and covered with blankets during the night, this extra space can be used for March plantings of cool-tolerant cutting greens, such as lettuce or mustards, sown directly in the cold-frame soil.

In late August, when the cold frame is not otherwise in use, I transplant lettuce, endive and mustards directly into the soil so the plants have enough time to reach full size before cold weather begins. Lettuces vary widely in their cold tolerance; I’ve had best success with cold-hardy varieties such as ‘North Pole’ and ‘Winter Marvel.’ Covering the cold frame at night with blankets may extend the season a few weeks longer, and endive is so hardy that harvest is still possible long after the plants remain totally frozen.

Storage around the House

Every house has places suitable for winter storage of vegetables that prefer moderate temperatures. In my Italian family, no kitchen would seem properly habitable if it didn’t have a long braid of garlic hanging on the wall not too far from the stove. Onions and winter squash also store well at room temperature, although I keep the bulk of the squash, onion and garlic crops in our cooler underground basement for longer keeping until the supplies dwindle upstairs. I keep boxes of sweet potatoes in the basement, too. Unlike potatoes, sweet potatoes do not have to be kept in the dark, so they could just as well be spread out on a shelf even if the basement has windows.

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Basement storage can be tricky. House-stored crops prefer a cool, dry environment. Some cellars are too damp and, if not well insulated, may be too cold; those housing a furnace may be too warm. A totally earth-sheltered, unheated basement stays at a constant 55 degrees year-round; if dry, this is probably the best place in the house to arrange storage space.

Experience will determine which of your favorite winter squash varieties keeps the longest. Some of the sweetest, such as ‘Sugar Loaf,’ also spoil the quickest (They’re well worth growing, though; just eat them first!), and ‘Valenciano’ holds my record so far for longest storage: more than two years! I also have succeeded in storing sweet potatoes in perfect condition more than a year and a half past harvest.

One stinky, rotten winter squash oozing through the floorboards is a quick reminder that all stored vegetables, upstairs or down, must be policed regularly for decay, though. I place each squash and onion on a thick bed of newspapers, which will absorb the juices in case a rotting one escapes notice now and then.

Root Cellar Storage

For all vegetables that require cold storage, a root cellar reigns supreme. A properly designed root cellar ensures an abundant supply of fresh vegetables from the last garden harvests or markets of autumn until May. Together with good keepers stored in the house, the last root-cellared vegetables easily meet up with the first greens that can be grown in spring, thus guaranteeing a full year’s supply of garden-fresh vegetables, even in a climate with eight months of winter.

Many designs have been tried over centuries of root-cellaring history, but the main criteria remain constant: A temperature barely above freezing (33 to 35 degrees) must be achieved as quickly as possible in the fall and maintained as late as possible in spring, and humidity should be held somewhat in check. The best root cellars are usually constructed adjacent to or separate from the house, and far enough underground to be insulated against extreme winter cold but not so earth-sheltered that the 55-degree ground temperature keeps the space too warm. An airlock between inner and outer doors provides further temperature regulation, and two closeable vents, one low to let in cold night air and one in the ceiling to let warmer air escape, allow the space to cool quickly in the fall, then be sealed for winter. All openings must be rodent-proof; failing that, rodent vigilance must be rigorously maintained.

Keeping humidity down is a harder problem to solve. A full root cellar, especially one filled with potted plants that need occasional watering, generates a lot of moisture that condenses on concrete walls and ceilings. A dry earthen floor helps to absorb excess moisture and is preferable to concrete. Some folks also prefer a wooden root cellar with a well-insulated attic rather than an earth-covered concrete roof, thus insuring that the space breathes and moisture can escape.

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Vegetables we store in the root cellar fall into three broad categories: root crops, green vegetables replanted in containers and those grown in containers in the first place. In addition, most storage vegetables are biennials that can be planted out again the following spring for seed-saving purposes.

The easiest and best-known root cellar crops are, as the name implies, the root vegetables. Of all these, potatoes are unique in being frost-tender; they alone determine that the root cellar never be allowed to dip below freezing, even though temperatures just above freezing are perfect for long-term storage without sprouting. The tubers may be kept in boxes or spread out on shelves. Since potatoes gradually turn green when exposed to light and thus begin to produce the same toxins that make potato plants poisonous, the darkness of a root cellar is perfect for storing them. One word of caution, however: If your root cellar has a tendency to freeze during very cold spells, leaving one 100-watt light bulb burning constantly may keep the space tempered, but that same light will turn your potatoes green. If you choose this step, keep your potatoes in closed or covered boxes.

All other root crops must be covered in such a way that they will stay moist and crisp. Any containers made of wood, metal or plastic will do. I have used sand, sawdust or fine wood chips, and finely chipped leaves as storage media with equal success. I began my experimentation by slightly moistening the medium before packing the roots: I’ve found, however, that a container amply filled with roots generates enough moisture to keep all roots fresh if they stay covered in the medium. Excess moisture only encourages decay. Jerusalem artichokes present the one exception to this rule; they must be stored in a moist medium in order to stay crisp through winter.

Carrots, beets, rutabagas, turnips, winter-storage radishes, celeriac and parsnips can all be stored in this way, and preparation for all of them is the same. Dig the roots in the fall after some frost has fully developed flavor but before night temperatures drop much below the mid-20s. Damage from really hard frosts can cause spoilage in storage later.

On celeriac, cut off all foliage just above the crown, being careful not to cut into the tender apical bud itself, and remove excess roots. My next step is to wash the roots by spreading them out on the lawn and hosing off both sides, allowing them to drain and partially dry. Any roots injured in digging, and any that are deformed or woody, are sorted out for fresh eating or discarded. At this time, I usually pick out a good selection of roots from each variety I intend to save seed from for the following year (about two dozen in order to maintain genetic viability), label them and store them separately in gunnysacks of sawdust or chipped leaves. The rest are layered on a bed of the storage medium, covered enough so that no root touches any other to retard the spread of decay should it occur and further layered until the containers are full.

Seed Plants

For the purpose of saving seed, roots of mature Swiss chard may be dug in the fall and stored in the same way as root crops. I also have successfully maintained artichokes as a viable annual crop far beyond their normal range here in Iowa by digging the perennial plants in the fall, storing them this same way, then planting them out again just as soon as the ground can be worked in the spring.

Leeks and cabbage are two crops with a long history of winter storage. Long-season, firm-headed cabbages have been developed, mostly in Europe, specifically for this purpose and are much preferred as long keepers. Cabbages have often been stored by hanging the heads from their stems, but I have discovered that replanting works much better, keeping them totally garden crisp for a full seven months.

As I dig the plants in the garden, I strip off all the leaves until only the tight heads remain on the stem, then replant as many as I can fit in a single plastic 5-gallon pot (or, if the heads are large, I fit as many as I can carry, since a pot full of cabbage plants can be quite heavy), firmly covering the roots with garden dirt. I use these same containers for leeks, knocking excess dirt from the roots, cutting off about a third of the leafy tops and removing dead leaves to reduce decay in storage. Then I pack them into the pot, covering their roots as I go, until I’ve fitted as many in as the container can hold. I water the dirt thoroughly around the roots and let the pots drain well before placing them in the root cellar. In fact, if the cellar isn’t down to temperature yet, I will leave my cold-hardy vegetables outside a while longer, covering them at night with blankets if necessary, until my cellar has cooled sufficiently. The longer green vegetables can stay out in the light, the better.

Our most exciting discovery has been achieving long-term storage of the more fragile winter vegetables, especially radicchio and Chinese cabbages. Any solid-heading type of Napa cabbage will do the trick, but hybrid varieties such as ‘Blues’ or ‘Komatsuna’ developed specifically for fall production work the best. I also choose fall-heading varieties of radicchio like ‘Augusto,’ ‘Chioggia Preco No. 1’ or ‘Rossana.’ In northern Iowa, these varieties must be planted right around the Fourth of July so they are fully headed by the advent of cold weather. Then they must be harvested before temperatures fall much below the mid-20s.

The best storage containers I have found for these crops are plastic kitty litter trays available in any supermarket or pet store. As I dig these fragile winter vegetables in the garden, I remove outer leaves from any heads that seem full and hard enough to endure storage, saving others for more immediate use. I pack the winter keepers in the trays, filling around their roots with garden soil, until the trays are full. Water them lightly (because there are no drain holes in these trays, do not overwater!) and that’s it. They are ready for storage. I treat kohlrabis, another great winter storage vegetable that keeps perfectly until spring, exactly the same way.

All of these replanted crops, especially heads of cabbage, Chinese cabbage and radicchio, will gradually slime black with decay on the outside as winter progresses. Do not be alarmed — you will be amazed how the removal of only a single layer of leaves reveals a perfect, fresh head beneath the surface. Radicchio is the hardest to store, and some heads will rot faster than you can use them, so just grow extra.

For seed-saving purposes, kale and collard plants can be dug in the fall, stripped of all leaves down to the tiny apical few, and replaced just like cabbage, then set out again in the spring. In fact, all cabbage stems whose heads have been cut in winter can be planted out; they will branch profusely and produce ample seed the following season.

Less well known is that kale, collards and parsley can be grown to maturity in large pots and placed in the root cellar in full leaf, and all those green leaves will stay green and perfectly fresh all winter, available for harvest whenever you desire! At 33 degrees, no further growth occurs; white leaves will begin to grow in the dark only toward spring as the cellar begins to warm up. By then, the plants can be replanted outside and left to bloom for seed-saving. I have had longer harvests of these leafy greens from the root cellar than from a sunny window in the house because, at room temperature, biennials continue to grow and soon begin to bolt to premature flower.

All containerized plants in the root cellar must have their water needs checked from time to time. Since too much humidity is usually the prevailing condition, pots seldom dry out, but if any do, just add a little water. I’ve found that one or two spot waterings throughout the winter usually keeps things alive until warmer temperatures arrive.

Using all of these techniques to store fresh vegetables, we manage to keep an array of fresh produce all winter long here in the North. We still bottle tomatoes, salsa, applesauce and other fruit, and freeze our berries, corn, beans, peppers and broccoli, yet each year we are amazed how little we rely on our processed vegetables in favor of eating fresh ones, a fair amount of “California living” in Iowa.

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